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-Structure paper
Title | Mechanism of human Lig1 regulation by PCNA in Okazaki fragment sealing. |
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Journal, issue, pages | Nat Commun, Vol. 13, Issue 1, Page 7833, Year 2022 |
Publish date | Dec 20, 2022 |
![]() | Kerry Blair / Muhammad Tehseen / Vlad-Stefan Raducanu / Taha Shahid / Claudia Lancey / Fahad Rashid / Ramon Crehuet / Samir M Hamdan / Alfredo De Biasio / ![]() ![]() ![]() |
PubMed Abstract | During lagging strand synthesis, DNA Ligase 1 (Lig1) cooperates with the sliding clamp PCNA to seal the nicks between Okazaki fragments generated by Pol δ and Flap endonuclease 1 (FEN1). We present ...During lagging strand synthesis, DNA Ligase 1 (Lig1) cooperates with the sliding clamp PCNA to seal the nicks between Okazaki fragments generated by Pol δ and Flap endonuclease 1 (FEN1). We present several cryo-EM structures combined with functional assays, showing that human Lig1 recruits PCNA to nicked DNA using two PCNA-interacting motifs (PIPs) located at its disordered N-terminus (PIP) and DNA binding domain (PIP). Once Lig1 and PCNA assemble as two-stack rings encircling DNA, PIP is released from PCNA and only PIP is required for ligation to facilitate the substrate handoff from FEN1. Consistently, we observed that PCNA forms a defined complex with FEN1 and nicked DNA, and it recruits Lig1 to an unoccupied monomer creating a toolbelt that drives the transfer of DNA to Lig1. Collectively, our results provide a structural model on how PCNA regulates FEN1 and Lig1 during Okazaki fragments maturation. |
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Methods | EM (single particle) |
Resolution | 4.2 - 7.8 Å |
Structure data | EMDB-14078, PDB-7qnz: EMDB-14080, PDB-7qo1: ![]() EMDB-15385: FEN1 holoenzyme with a nicked DNA substrate EMDB-15921, PDB-8b8t: |
Chemicals | ![]() ChemComp-AMP: |
Source |
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![]() | REPLICATION / DNA / Complex / Ligase / PCNA / Ligation / Okazaki fragment maturation / FEN1 / Flap Endonuclease I |